Pipes and tubular conduits – Flexible – Spirally wound material
Patent
1987-04-08
1990-02-27
Recla, Henry J.
Pipes and tubular conduits
Flexible
Spirally wound material
138141, 138143, 138144, F16L 1100
Patent
active
049037358
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a pipe usable in particular for transporting fluids and allowing the permeability to the fluids transported, for example corrosive fluids, to be limited.
The invention relates in particular to the field of transporting liquid or gaseous fluids, particularly hydrocarbons, in pipes likely to be used at high pressure and high temperatures for long periods of time.
The application of the invention to the production of flexible pipes and rigid reinforced-resin pipes will be considered in particular below.
Here, flexible tubes or pipes are understood to be pipes having sufficient flexibility to accept (without deterioration) a radius of curvature R less than or equal to a.times.d, wherein d is the diameter of the tube measured in the same unit as R and a is a numerical coefficient whose value does not exceed a few units, 4 to 5 for example.
A flexible pipe designed to operate under high pressure is composed for example of the following elements:
a folded metal strip designed to prevent the pipe from being crushed by the pressure differential between the inside and the outside;
a flexible inner sheath made of plastic or elastomer, making the pipe largely impermeable on the inside;
at least one reinforcing layer to withstand tensile and/or internal pressure forces, and
a second flexible plastic or elastomer sheath to ensure external impermeability of the pipe.
A rigid pipe designed to operate under high pressure is composed for example of the following elements:
a soft, inner, highly flexible sheath
an outer sheath formed by winding fibers pre-impregnated with a thermosetting resin.
The problems involved in transportation of liquid or gaseous fluids at high temperatures and pressures in these types of pipes are linked to the permeability of the products used.
For flexible pipes, these problems are (1) permeability of the material of which the inner sealing sheath is composed, whereby this permeability increases very substantially with temperature and pressure, and (2) accumulation of gas between the inner and outer sheaths due to the fact that the permeability of the outer sheath may be far less than that of the inner sheath.
Particularly in the case of transporting liquid or gaseous hydrocarbons likely to contain corrosive agents such as H.sub.2 S, CO.sub.2, etc., this accumulation may cause accelerated corrosion of the metal reinforcements.
In addition, the pressure prevailing between the two sealing layers may become greater than the external pressure applied to the flexible pipe and cause the outer sheath to shatter.
Moreover, these permeability phenomena result in varying degrees of loss of transported fluid.
For rigid pipes, these problems are due to the limited flexibility of the pipes which causes microcracking under mechanical stress, which can lead to "sweating" of the fluid.
It is known that the use of continuous corrugated metal in a flexible pipe instead of the plastic inner sheath avoids the drawbacks inherent in plastic sheaths, but this solution has the drawback of great sensitivity to corrosion, the corrugated metal being in direct contact with the fluid. Moreover, the geometry of the metal can disturb the flow of the fluids or passage of any special tools (measuring or cleaning tools for example) through the pipe.
European patent application EP-A-0.111.169 relates to a multi-layer gastight tube. It has in particular a metal envelope integral with the outer periphery of a plastic sheath and with the inner periphery of an outer tube. The integral assembly is spiral-wound edge to edge, either hot such as to form a seal with the plastic sheath which has been softened, or by means of a cold-setting or hot-setting cement. This edge-to-edge winding technique of layers which are integral with each other can only be applied to rigid tubes and not to flexible tubes which would then lose all their flexibility.
The prior art of pipe-making techniques is illustrated for example by patents FR-A-2.467.347 or EP-A-0.068.128.
When applied to flexible tubes, the present invention a
REFERENCES:
patent: 3604461 (1971-09-01), Matthews
patent: 4403631 (1983-09-01), Abdullaev et al.
Dawans Francois
Delacour Jacques
Dewimille Bernard
Jarrin Jacques
Barrett Glenn T.
Institut Francais du Pe'trole
Recla Henry J.
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